Absorbent articles of the present kind often comprise a liquid-pervious cover sheet topsheet that is located adjacent the wearer's body, a liquid-impervious cover sheet (backsheet) that is located distant from the wearer's body and adjacent the wearer's clothing and an absorbent layer interposed between the liquid-pervious topsheet and the liquid-impervious backsheet.
It is customary to use nonwovens and perforated film materials as topsheets. Both materials are generally made from inherently hydrophobic, synthetic polymers such as polyethylene or polypropylene.
Hydrophobic materials show almost no tendency to absorb body fluids on the surface so that after passage of body fluids and their absorption by the absorbent layer the surface develops a rather pleasant dry feel for the user. Since hydrophobic materials frequently suffer from insufficient wettability it is known to treat them with wetting agents, for instance surfactants to enhance the contact with water and liquid permeability. However, due to their capacity to bind water, hydrophilic materials tend to lead to an undesired wet feel upon discharge of body fluids.
Completely hydrophilic or hydrophobic materials are thus not capable of satisfying conflicting needs of the wearer of an absorbent article. Such materials also do not allow making use of their beneficial properties where they are mostly needed. Moreover, it is believed that neither fully hydrophobic nor fully hydrophilic materials are capable of promoting a healthy climate in the absorbent article. As healthy climate we understand in particular a low humidity environment where, despite the release of body fluids or sweat, the skin of the wearer is not prone to overhydration which is one of the most frequent causes of diaper rash.
Moreover, nanoscalar films of self-assembling polymers are known from various technical fields and have attracted considerable interest over the last years. These nanoscalar films are typically formed by the alternate deposition of monomolecular layers of two polymers having functional groups capable of interacting with each other. A great deal of these studies has been conducted with the layer-by-layer deposition (also abbreviated as LBL deposition) of cationic and anionic polymers based on the reversal of the surface charge after each deposition, one of the best-examined systems being poly(styrene sulfonate)/(polyallylamine hydrochloride) (PSS/PAH).
US 2005/0069950 A1 discloses a method for the nanofabrication of thin films, coatings and microcapsules based on suitable design of oligopeptides. Drug delivery is discussed in connection with microcapsules. Moreover, disposable diapers are mentioned as one among many possible uses for peptides designed according to this document. More concretely described are biomedical applications.
U.S. Pat. No. 5,807,636, U.S. Pat. No. 5,700,559 and U.S. Pat. No. 5,837,377 relate to a hydrophilic article for use in aqueous environments including a substrate, an ionic polymeric layer on said substrate and a disordered polyelectrolyte coating ionically bonded to said polymeric layer. Diapers and other liners are mentioned as one among many potential applications of this teaching.
WO 00/32702 describes for instance a paper or nonwoven product containing fibers, filler particles or other particles produced by the layer-by-layer deposition of two interacting polymers, preferably anionic and cationic polyelectrolytes which are typically used as dry and wet strength agents in the paper manufacture. Accordingly, this document also evaluates the tensile strength of the paper product.
Further documents relating to LBL technology are for instance: WO 2005/058199 A1; U.S. Pat. No. 5,208,111; U.S. Pat. No. 5,518,767; U.S. Pat. No. 5,536,573; U.S. Pat. No. 6,114,099; U.S. Pat. No. 6,451,871; U.S. Pat. No. 6,492,096; US 2003/152703; US 2004/0086709; WO 2005/032512; US 2004/0137039; “A. A. Antipov et al., Sustained Release Properties of Polyelectrolyte Multilayer Capsules; J. Phys. Chem. B 2001, 105, 2281-2284”; “M. Freemantle, Polyelectrolyte Multilayers; Science & Technology (2002), 44-48”; US 2004/0047979 A1; U.S. Pat. No. 5,885,753; and WO 2004/07677 A2.
There is also one document relating to multilayer construction in diapers without connection to LBL. WO 2005/023536 discloses an absorbent article comprising at least one first microlayer film region having a liquid intake function, at least one second microlayer film region having a liquid uptake and distribution function, at least one third microlayer film region having a liquid retention function, and at least one fourth microlayer film region having a liquid barrier function. These first, second, third and fourth microlayer film regions are co-extruded and assembled with each other to form the unitary micro-layered film system. However, these layers apparently have a thickness above the nm range and do not assemble themselves.
In view of the above, it is one technical object of the present disclosure to provide an absorbent article wherein the disadvantages of using fully hydrophobic or fully hydrophilic materials are avoided or alleviated.
It is one further technical object of the present disclosure to make a more efficient use of hydrophilic and hydrophobic material properties.
It is one further technical object of the present disclosure to provide an absorbent article wherein certain parts thereof can contribute in a beneficial manner to at least one relevant property such as material feel, fluid transport, healthy climate within the absorbent article or the like.